Communication method and apparatus using network slicing

ABSTRACT

Provided is a communication method and apparatus using network slicing. A communication method of a communication apparatus performing communication with a user equipment receives a predetermined request from the user equipment, selects a single network slice instance to be allocated to the user equipment from among a plurality of network slice instances in the communication apparatus in response to the request, selects a single network function instance to be allocated to the user equipment from among a plurality of network function instances included in the selected network slice instance. The network slice instance is in an instantiated form of a network slice that includes at least one network function and resource for providing a network service having a predetermined capability and characteristic to the user equipment.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the priority benefit of Korean PatentApplication No. 10-2016-0047216 filed on Apr. 18, 2016, Korean PatentApplication No. 10-2016-0107022 filed on Aug. 23, 2016, and KoreanPatent Application No. 10-2017-0048448 filed on Apr. 14, 2017 in theKorean Intellectual Property Office, the disclosures of which areincorporated herein by reference for all purposes.

BACKGROUND 1. Field

At least one example embodiment relates to a communication method andapparatus using network slicing, and more particularly, to acommunication method and apparatus for selecting a network sliceinstance and a network function instance for providing a network serviceto a user equipment.

2. Description of Related Art

5G network technology may be 5^(th) generation mobile communicationtechnology that is redesigned into an end-to-end (E2E) convergencenetwork architecture to support various devices and various services assucceeding technology of 4^(th) generation long term evolution (LTE)mobile communication technology. The 5G network technology is expectedto be an E2E system in which all of targets, for example, technology,domain, hierarch, equipment/device, user interaction, etc., of a networkconnected using a variety of methods including a wired manner are highlyconverged.

SUMMARY

At least one example embodiment may provide a communication method andapparatus using network slicing that may select a network slice instanceand a network function instance corresponding to a network servicerequested from a user equipment, and may provide the requested networkservice to the user equipment through network slicing. At least oneexample embodiment may also provide a communication method and apparatususing network slicing that may provide the flexibility of a 5G corenetwork architecture according to the introduction of networkvirtualization technology, and enables a network provider to achieve theeffectiveness maximization and cost reduction according to a networksystem and resource management.

According to an aspect of at least one example embodiment, there isprovided a communication method of a communication apparatus performingcommunication with a user equipment, the method including receiving apredetermined request from the user equipment; selecting a singlenetwork slice instance to be allocated to the user equipment from amonga plurality of network slice instances in the communication apparatus inresponse to the request; and selecting a single network functioninstance to be allocated to the user equipment from among a plurality ofnetwork function instances included in the selected network sliceinstance. The network slice instance is in an instantiated form of anetwork slice that includes at least one network function and resourcefor providing a network service having a predetermined capability andcharacteristic to the user equipment.

The selecting of the network slice instance may include selecting thenetwork slice instance to be allocated to the user equipment based onnetwork slice selection assistance information (NSSAI) included in therequest.

The NSSAI may include a slice/service type (SST) requested from the userequipment or the slice/service type and a slice differentiator (SD)corresponding to the user equipment.

The slice/service type may indicate an expected network behavior interms of a service requested from the user equipment.

The slice differentiator may complement the slice/service type to selecta single network slice instance from among a plurality of network sliceinstances that comply with the slice/service type, in response to theplurality of network slice instances complying with the slice/servicetype.

The slice differentiator may include at least one of a registration areain which the user equipment is located, subscription of the userequipment, quality of service (QoS) attributes of the plurality ofnetwork slice instances requested, and a terminal characteristic.

The selecting of the network slice instance may include selecting thenetwork slice instance to be allocated to the user equipment by furtherusing at least one of a network slice instance pre-allocated to the userequipment and a serving registration area of the user equipment.

The selecting of the network function instance may include selecting thenetwork function instance to be allocated to the user equipment based ona logical network identifier indicating the selected network sliceinstance and a type of a network function indicating a role of thecorresponding network function instance.

The selecting of the network function instance may include selecting asingle network function instance for each type of the network functionamong the plurality of network function instances included in theselected network slice instance.

The selecting of the network function instance may include selecting thenetwork function instance to be allocated to the user equipment byfurther using a policy of a network operator that provides the networkslice instance.

The selecting of the network function instance may include selecting thenetwork function instance based on a selection condition received by aserving network function repository function (NRF) corresponding to theselected network slice instance from a source-network function instance(S-NFI) that requests the selection of the network function instance.

The selecting of the network function instance may include selecting, bya source-network function instance (S-NFI) receiving a selectablenetwork function instance list from a serving network functionrepository function (NRF) corresponding to the selected network sliceinstance, the network function instance and forwarding information aboutthe selected network function instance to the serving NRF.

According to another aspect of at least one example embodiment, there isprovided a communication method of a communication apparatus performingcommunication with a user equipment, the method including receiving apredetermined request from the user equipment; selecting a singlenetwork slice instance to be allocated to the user equipment from amonga plurality of network slice instances in the communication apparatus inresponse to the request; and forwarding a response to the request to theuser equipment in response to the selection of the network sliceinstance. The network slice instance is in an instantiated form of anetwork slice that includes at least one network function and resourcefor providing a network service having a predetermined capability andcharacteristic to the user equipment.

The selecting of the network slice instance may include selecting thenetwork slice instance to be allocated to the user equipment based onnetwork slice selection assistance information (NSSAI) included in therequest.

The communication method may further include performing relocation froma current access and mobility management function (AMF) to a new AMF inresponse to a detection of the new AMF further appropriate compared tothe current AMF, to provide the selected network slice instance to theuser equipment.

An AMF and a network slice selection function (NSSF) included in thecommunication apparatus may be shared by a plurality of network sliceinstances allocated to the user equipment in response to the pluralityof network slice instances being allocated to the user equipment.

According to another aspect of at least one example embodiment, there isprovided a communication apparatus including a processor; and a memoryincluding at least one instruction executable at the processor. Inresponse to an execution of the at least one instruction at theprocessor, the processor may be configured to receive a predeterminedrequest from a user equipment, to select a single network slice instanceto be allocated to the user equipment from among a plurality of networkslice instances in the communication apparatus in response to therequest, and to select a single network function instance to beallocated to the user equipment from among a plurality of networkfunction instances included in the selected network slice instance, andthe network slice instance may be in an instantiated form of a networkslice that includes at least one network function and resource forproviding a network service having a predetermined capability andcharacteristic to the user equipment.

The processor may be configured to select the network slice instance tobe allocated to the user equipment based on network slice selectionassistance information (NSSAI) included in the request.

The processor may be configured to select the network slice instance tobe allocated to the user equipment by further using at least one of thenetwork slice instance allocated to the user equipment and a servingregistration area of the user equipment.

According to another aspect of at least one example embodiment, there isprovided a communication apparatus including a processor; and a memoryincluding at least one instruction executable at the processor. Inresponse to an execution of the at least one instruction at theprocessor, the processor is configured to receive a predeterminedrequest from a user equipment, to select a single network slice instanceto be allocated to the user equipment from among a plurality of networkslice instances in the communication apparatus in response to therequest, and to forward a response to the request to the user equipmentin response to the selection of the network slice instance, and thenetwork slice instance is in an instantiated form of a network slicethat includes at least one network function and resource for providing anetwork service having a predetermined capability and characteristic tothe user equipment.

According to example embodiments, it is possible to provide a requestednetwork service to a user equipment through network slicing by selectinga network slice instance and a network function instance correspondingto the network service requested from the user equipment.

Also, according to example embodiments, it is possible to provide theflexibility of a 5G core network architecture according to theintroduction of network virtualization technology, and to enable anetwork provider to achieve the effectiveness maximization and costreduction according to a network system and resource management.

Additional aspects of example embodiments will be set forth in part inthe description which follows and, in part, will be apparent from thedescription, or may be learned by practice of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects, features, and advantages of the inventionwill become apparent and more readily appreciated from the followingdescription of example embodiments, taken in conjunction with theaccompanying drawings of which:

FIG. 1 illustrates a reference architecture for network slicingaccording to an example embodiment;

FIG. 2 illustrates an architecture of a network slice according to anexample embodiment;

FIG. 3 illustrates an example of a network slice instance and a serviceinstance according to an example embodiment;

FIG. 4 illustrates an example of a service instance according to anexample embodiment;

FIG. 5 illustrates an example of selecting a network slice instance in auser equipment registration procedure according to an exampleembodiment;

FIG. 6 illustrates an example of selecting a network slice instance anda network function instance in a protocol data unit (PDU) sessionestablishment procedure according to an example embodiment;

FIG. 7 illustrates an example of a repository according to an exampleembodiment;

FIGS. 8 through 10 illustrate examples of selecting a network sliceinstance and a network function instance in a network slicingarchitecture according to an example embodiment;

FIG. 11 is a diagram illustrating a communication apparatus according toan example embodiment; and

FIGS. 12 and 13 are flowcharts illustrating a communication methodaccording to an example embodiment.

FIG. 14 is a flowchart illustrating NF Discovery service according to anexample embodiment.

FIG. 15 is a flowchart illustrating NF Discovery service across PLMNsaccording to an example embodiment.

DETAILED DESCRIPTION

Hereinafter, some example embodiments will be described in detail withreference to the accompanying drawings. Regarding the reference numeralsassigned to the elements in the drawings, it should be noted that thesame elements will be designated by the same reference numerals,wherever possible, even though they are shown in different drawings.Also, in the description of embodiments, detailed description ofwell-known related structures or functions will be omitted when it isdeemed that such description will cause ambiguous interpretation of thepresent disclosure.

The following detailed structural or functional description of exampleembodiments is provided as an example only and various alterations andmodifications may be made to the example embodiments. Accordingly, theexample embodiments are not construed as being limited to the disclosureand should be understood to include all changes, equivalents, andreplacements within the technical scope of the disclosure.

Terms, such as first, second, and the like, may be used herein todescribe components. Each of these terminologies is not used to definean essence, order or sequence of a corresponding component but usedmerely to distinguish the corresponding component from othercomponent(s). For example, a first component may be referred to as asecond component, and similarly the second component may also bereferred to as the first component.

It should be noted that if it is described that one component is“connected”, “coupled”, or “joined” to another component, a thirdcomponent may be “connected”, “coupled”, and “joined” between the firstand second components, although the first component may be directlyconnected, coupled, or joined to the second component. On the contrary,it should be noted that if it is described that one component is“directly connected”, “directly coupled”, or “directly joined” toanother component, a third component may be absent. Expressionsdescribing a relationship between components, for example, “between”,directly between”, or “directly neighboring”, etc., should beinterpreted to be alike.

The singular forms “a”, “an”, and “the” are intended to include theplural forms as well, unless the context clearly indicates otherwise. Itwill be further understood that the terms “comprises/comprising” and/or“includes/including” when used herein, specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components and/or groups thereof.

Unless otherwise defined, all terms, including technical and scientificterms, used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure pertains. Terms,such as those defined in commonly used dictionaries, are to beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art, and are not to be interpreted in anidealized or overly formal sense unless expressly so defined herein.

The following example embodiments may be used to perform communication.Hereinafter, an operation of performing communication may include anoperation of selecting at least one network slice instance (NSI) fromamong a plurality of network slice instances (NSIs) in a communicationapparatus, and an operation of selecting a single network functioninstance (NFI) from among a plurality of network function instances(NFIs) included in the selected network slice instance. The exampleembodiments may be configured as various types of computing devicesand/or systems, for example, a smartphone, a smart electronic device, apersonal computer, a laptop computer, a tablet computer, a wearabledevice, etc., which constitutes a user equipment (UE), a server, etc.,which constitutes a network, and the like. The example embodiments willbe described with reference to the accompanying drawings. Like referencenumerals refer to like elements throughout.

FIG. 1 illustrates a reference architecture for network slicingaccording to an example embodiment.

FIG. 1 illustrates a core part 100 of a network slice in the referencearchitecture according to an example embodiment.

In the case of network slicing, a control plane of the core part 100 ofthe network slice may include two parts, for example, a common controlpart and a slice-specific part. Network functions within the commoncontrol part may be shared by multiple slice instances, whereas networkfunctions within the slice-specific part may be dedicated to a specifictarget slice instance.

The reference architecture of FIG. 1 may be a network slicingnon-roaming service-based architecture. Due to network slicing, anetwork slice selection function (NSSF) 110 corresponding to anadditional network function may be added to the architecture that isspecific to a network slicing deployment to support a network sliceselection. More details on the functionality of the NSSF 110 will bedescribed below.

A control plane network function that has a darker shadow may be acandidate to reside in the common control part or the slice-specificpart. A control plane network function that does not have the darkershadow may be included in only the common control part. A method ofincluding the control plane network function having the darker shadow inthe common control part or the slice-specific part depending on a targetnetwork service supported by a network slice instance may follow adecision of an operator.

Here, a network function may be implemented either as a network elementon dedicated hardware or as a software instance running on dedicatedhardware, or may be implemented as a virtualized function instantiatedon an appropriate platform, for example, on a cloud infrastructure.

An access and mobility management function (AMF) 120 may include thefollowing functions. A portion of or all of the functions of the AMF 120may be supported by a single instance of the AMF 120.

-   -   Termination of RAN CP interface (N2)    -   Termination of NAS (N1), NAS ciphering and integrity protection    -   Registration management    -   Connection management    -   Reachability management    -   Mobility management    -   Lawful intercept (for AMF 120 events and interface to LI system)    -   Transparent proxy for routing SM messages    -   Access authentication    -   Access authorization    -   Security anchor function (SEA). The SEA may interact with an        authentication server function (AUSF) and a UE, and may receive        an intermediate key that is set as a result of a UE        authentication process. In the case of universal subscriber        identify module (USIM)-based authentication, the AMF 120 may        retrieve security materials from the AUSF.    -   Security context management (SCM). The SCM may receive, from the        SEA, a key used to derive an access network specific key.

Here, regardless of the number of network functions, a single non-accessstratum (NAS) interface instance is present per radio access network(RAN) between the UE and a control network (CN), and terminated at oneof network functions that implement at least NAS security and mobilitymanagement.

Once network slicing is deployed, the AMF 120 may interact with the NSSF110 over a network slice interface and a network slice instance may beselected. The network slice instance selection (NSI selection) will befurther described below.

Here, network slicing technology may indicate technology capable ofapplying network isolation and customization attributes to a mobilecommunication core network architecture by grouping and therebyproviding network resources and network functions into a singleindependent slice based on a service. The network slicing technology, asa new concept of a 5G core network not used in the existing mobilecommunication network technology, may be technology for grouping andthereby providing network resources and network functions required for aservice requested from a mobile terminal into a single independentslice.

In this manner, each network provider may independently allocate anetwork resource specified for each service and user, and may secure theexpandability and reliability of service and network resource operationby achieving the network flexibility through software definednetworking/network function virtualization (SDN/NFV) technology-basedresource virtualization.

Hereinafter, the network slicing technology will be described withreference to FIG. 2.

FIG. 2 illustrates an architecture of a network slice according to anexample embodiment.

Referring to FIG. 2, network slice instances are allocated to a UE.

The network slice may be a complete logical network that includes a setof network functions and corresponding resources required to provide aspecific network capability and network characteristic. The networkslice may be present on a radio access network (RAN) 220 and a corenetwork (CN) 230. A network slice instance may be the instantiation ofthe network slice, that is, a deployed set of network functions thatdeliver intended network slice services according to a network slicetemplate.

An AN may be common for multiple network slices. For example, the AN maybe a non-3GPP access network or a 5G RAN.

The network slice may be configured to be different for each supportedfeature and network function optimization. An operator may deploy theplurality of network service instances that deliver exactly the sameoptimization and features, however, dedicated to different groups basedon UE characteristics.

For example, referring to FIG. 2, a plurality of network slice instances240 and 250 may be allocated to the UE 210. The network slice instances240 and 250 may be defined on the RAN 220 and the CN 230. For example,the network slice instance 240 may include a RAN part 241 and a CN part243. The CN part 243 may include a common control network function(CCNF), a slice-specific control network function (SCNF), user planefunctions (UPFs), and others.

Each network slice instance may include at least one network functioninstance for providing a network service required for a correspondingnetwork slice instance. For example, the network slice instance 240 maybe for a multimedia service and the network slice instance 250 may befor an Internet of Things (IoT) service.

The UE 210 may simultaneously access the plurality of network sliceinstances 240 and 250 through a single RAN 220. In this case, thenetwork slice instances 240 and 250 may share a portion of control planefunctions, for example, an AMF 260 and an NSSF 270. A control planefunction shared by the plurality of network slice instances 240 and 250allocated to the same UE 210 may be referred to as the CCNF.

For example, the UE 210 may use only a single AMF 260. That is, a singleUE 210 may not be allowed to use two or more AMFs. Conversely, a singleAMF 260 may be allocated to one or more UEs. FIG. 2 illustrates a casein which a single AMF 260 is allocated to a single UE 210 as an example.

The AMF 260 and the NSSF 270 included in the CCNF may be shared betweenthe plurality of network slice instances 240 and 250 through NF sharing.

Also, an authentication function (AUF) and a policy control function(PCF) may be shared between one or more network slice instances based onan operator's policy through NF sharing.

Similar to the AMF 260, the NSSF 270 is a function included in the CCNF,and used to select a network slice instance corresponding to the UE 210.

The NSSF 270 may be a network function that has knowledge and overviewof an NSI topology for a given public land mobile network (PLMN) (forexample, recognizing the availability of a set of active network sliceinstance(s) corresponding to registration areas and for which entrypoint, that is, the AMF 260, that is accessible to a specific networkslice instance). Also, the NSSF 270 may support a slice-level servicemapping for given single-network slice selection assistance information(S-NSSAI) to select a target network slice instance based on a servingmobile virtual network operator (MVNO), a service or an over the top(OTT) provider, a UE location, a time window, and the like. Here, thetarget network slice instance may be selected from a pool of networkslice instances for specific S-NSSAI for load balancing and redundancy.

The NSSF 270 may enforce operator configured slice-level control rules.For example, to provide mission-critical services, such as an autonomousdriving or a remote industrial robot control, a network slice instancethat guarantees low-latency access needs to be acquired.

The NSSF 270 may support a statistic collection for a slice selectionfor a management system of the serving PLMN.

The following parameters may be used to perform communication with theAMF 260 based on the aforementioned understanding about the NSSF 270.

An input parameter of the NSSF 270 may include accepted S-NSSAI.Additionally, depending on cases, at least one of a previous related NSIlist of the UE 210 and a serving registration area of the UE 210 may befurther considered as the input parameter of the NSSF 270.

An output parameter of the NSSF 270 may include information, forexample, an NSI ID, about a selected new serving network slice instancecorresponding to the accepted S-NSSAI. Additionally, depending on cases,at least one of a fully qualified domain name (FQDN) or an IP address ofa selected new serving AMF and an FQDN or an IP address of a selectedserving NF repository function (NRF) for a selected network sliceinstance may be further considered as the output parameter of the NSSF270.

In the case of network sharing, each PLMN may include its ownprovisioned network slice instance and corresponding NRF to support NFdiscovery and selection within a network slice instance. Also, inaddition to a type of a network function as the input parameter, alogical network identifier may be provided to the NRF for the NFdiscovery and selection so that the NRF may support a network functiondiscovery and selection operation regardless of whether network slicingis present. In the case of network slicing, the logical networkidentifier indicates an NSI ID and otherwise, the logical networkidentifier indicates a serving PLMN.

FIG. 3 illustrates an example of a network slice instance and a serviceinstance according to an example embodiment.

FIG. 3 illustrates a network slice instance 310 and a service instance320 according to an example embodiment.

At least one network slice instance 310 may be defined in a networksystem. One of the at least one network slice instance 310 may beselected to provide a service requested from a UE. Details on an NSIselection will be described below.

The network slice instance 310 may be a set of network functioninstances ready to support a network service requested from the UE. Atleast one network function instance may provide the same networkfunction, for example, a session management function (SMF), within thenetwork slice instance 310. When a plurality of network functioninstances provides the same network function within the same networkslice instance 310, a single network function instance may be selectedfrom among the plurality of network function instances. Details on anNFI selection will be described below.

A single network slice instance 310 may be allocated to at least one UEand may also be allocated to at least one service. The network sliceinstance 310 may correspond to a resource group per service of anoperator.

The service instance 320 may be a set of serving network functioninstances that support a service requested from the UE. The serviceinstance 320 may include each network function required for acorresponding service. The service instance 320 may indicate a networkslice instance substantially allocated to the UE.

FIG. 4 illustrates an example of configuring a service instanceaccording to an example embodiment.

A process of configuring a service instance 430 through an NSI selection410 and an NFI selection 420 according to an example embodiment will bedescribed with reference to FIG. 4.

In the NSI selection 410, a single network slice instance may beselected from among a plurality of network slice instances in a networksystem. Here, the network slice instance may be selected based on NSSAI.Additionally, the network slice instance may be selected by furtherusing a network slice instance previously allocated to a UE and aserving registration area of the UE. An available NSI ID may be outputas a selection result. Additionally, at least one of IP addresses of anew AMF and a serving NRF for the selected network slice instance may befurther output. It will be further described.

In the NFI selection 420, a single network function instance may beselected from among a plurality of network function instances within theselected network slice instance. Here, the network function instance maybe selected based on a logical network identifier and a type of anetwork function. The logical network identifier indicates an NSI ID inthe case of network slicing, and otherwise, indicates a serving PLMN.The type of the network function indicates a role of a correspondingnetwork function instance and may include, for example, an AMF, an NSSF,an SMF, a UPF, an AUF, a PCF, and the like. A single network functioninstance may be selected per type of a network function required toprovide the network service requested from the UE.

For example, referring to FIG. 4, a plurality of SMFs may be presentwithin a selected network slice instance. Even using the logical networkidentifier, that is, the selected NSI ID, and the type of the networkfunction, that is, the SMF, one or more network function instances maybe selected. If plurality of network function instances are selected,the operator's policy may be additionally considered in order to selecta single network function instance. The operator's policy refers to apolicy set by a network operator and may include, for example, loadbalancing, resource optimization, energy efficiency, trafficoptimization, and the like.

For example, an SMF having the relatively small number of currentlyusing UEs may be selected from two SMFs. Alternatively, an SMF having arelatively excellent QoS may be selected from the two SMFs.Alternatively, an SMF corresponding to a fee plan, for example, a basicfee plan and a premium fee plan, of a corresponding UE may be selectedfrom the two SMFs. Alternatively, an SW corresponding to a servingregistration area of the corresponding UE may be selected from the twoSMFs. Depending on cases, a network function instance may be selected byfurther using at least one of the aforementioned various criteria.

The service instance 430 may indicate a selected network slice instancethat includes the selected network function instance. The serviceinstance 430 may indicate a network slice instance capable of completelyproviding the network service requested from the UE.

Hereinafter, the NSI selection 410 and the NFI selection 420 will befurther described. The NSI selection 410 may be performed during a UEregistration procedure and a PDU session establishment procedure. TheNFI selection 420 may be performed during the PDU session establishmentprocedure.

If a network system deploys network slicing, at least one network sliceinstance may be selected based on NSSAI provided from the UE. The NSSAIis a set of S-NSSAIs. Each piece of S-NSSAI may be used to select aspecific network slice instance. In addition, UE capabilities and UEsubscription data may be used to select a network slice instance.

S-NSSAI may include a slice/service type (SST) and a slicedifferentiator (SD). Here, the SST refers to an expected networkbehaviour in terms of features and services. The SD refers to optionalinformation that complements the SST and may differentiate a pluralityof network slice instances that satisfy the SST.

The UE subscription data may include information about a network sliceinstance that the UE is allowed to access. Information within the UEsubscription data may include a plurality of pieces of S-NSSAI that theUE is allowed to use.

Also, the UE subscription data may include information regarding whethercorresponding S-NSSAI is default S-NSSAI. Here, the default S-NSSAI mayindicate a network slice instance that the UE is to use to attach to thenetwork system. When the UE makes an initial registration to the networksystem without providing any NSSAI in a registration request, a CN needsto use default NSSAI including S-NSSAI values stored in the UEsubscription data with a flag indicating that they are to be consideredas default, in order to determine a default initial network sliceinstance to serve the UE. Also, the UE subscription data may include adata network name (DNN) value for S-NSSAI.

A CN part of a network slice instance that serves the UE may be selectedby the CN, not by a RAN. The UE may simultaneously access a plurality ofnetwork slice instances through a single RAN. In this case, the networkslice instances simultaneously accessed by the UE may share a portion ofcontrol plane functions that include an AMF in the CN.

An AMF selection for a set of network slice instances for the UE may betriggered by a first contacted AMF in a registration procedure, whichmay lead to change of the AMF. Once a target network slice instance isselected and a session management (SM) message for establishing a PDUsession is received from the UE, a subsequent SMF network functiondiscover and selection may be initiated by the AMF. An NRF may be usedto perform the above selection tasks.

The PDU session may belong to a specific network slice instance.Although different network slice instances may not share the PDUsession, the different network slice instances may includeslice-specific PDU sessions to the same DNN.

The S-NSSAI may include standard values or PLMN-specific values. Theplurality of pieces of S-NSSAI with PLMN-specific values may beassociated with a PLMN ID of a PLMN that assigns the S-NSSAI in the UE.A single piece of S-NSSAI may not be used by the UE in access stratumprocedures in any PLMN other than the one with which the S-NSSAI isassociated.

The NSSAI may be used to select an AMF and a set of network sliceinstances, whereas the S-NSSAI may be used to select a specific networkslice instance. Each piece of S-NSSAI included in the NSSAI may include(a) an SST or (b) the SST and an SD.

The UE may store configured and/or accepted NSSAI per PLMN. Theconfigured NSSAI may be NSSAI configured in the UE by a home PLMN(HPLMN) to be used at the PLMN when no PLMN-specific accepted NSSAI isstored.

The accepted NSSAI refers to NSSAI provided from the PLMN to the UE, andthe UE needs to use the accepted NSSAI after the PLMN successfullyregisters the UE. A registration accept message may include the acceptedNSSAI. The accepted NSSAI may be updated through a subsequentregistration procedure.

If configured or accepted NSSAI of a PLMN that the UE accesses isprovided to the UE, the UE may provide the NSSAI in radio resourcecontrol (RRC) connection establishment and non-access stratum (NAS). TheRAN may route an initial access to the AMF using the provided NSSAI.

If the UE does not receive any accepted NSSAI of the PLMN that the UEaccesses and is provided with configured NSSAI, the UE may provide theconfigured NSSAI in the RRC connection establishment and NAS to the RAN.The RAN may use the NSSAI to route the initial access to the AMF.Alternatively, if the UE is not provided with any accepted NSSAI orconfigured NSSAI of the PLMN that the UE accesses, the UE may notprovide the NSSAI in the RRC connection establishment and NAS and theRAN may send NAS signalling to a default AMF.

A network operator may provide a network slice selection policy (NSSP)to the UE. The NSSP may include one or more NSSP rules each thatassociates an application with specific S-NSSAI. The NSSP may include adefault rule that matches all applications and includes default S-NSSAI.The UE may use the NSSP to associate a UE application with S-NSSAI.

When a UE application associated with specific S-NSSAI requests datatransmission, and in this instance, if the UE includes one or more PDUsessions established with the specific S-NSSAI and if the otherconditions of the UE do not prohibit the use of PDU sessions, the UE mayroute user data of the application in one of the PDU sessions. If theapplication provides a DNN, the UE may determine a PDU session to usebased on the DNN.

When the UE application associated with the specific S-NSSAI requeststhe data transmission, and in this instance, if the UE does not includea PDU session established with the specific S-NSSAI, the UE may requesta new PDU session with the S-NSSAI and the DNN that may be provided bythe application.

FIG. 5 illustrates an example of selecting an NSI in a UE registrationprocedure according to an example embodiment.

A communication method performed by a UE and a communication apparatuswill be described with reference to FIG. 5. In FIG. 5, the UE refers tothe user equipment and an AMF, a NSSF, a UDM, and a new AMF may indicatenetwork function instances included in the communication apparatus.

Referring to FIG. 5, in operation 501, the UE sends a registrationrequest to the AMF. The UE may send the registration request to the AMFwith one of default NSSAI, configured NSSAI, and accepted NSSAI througha RAN. Here, the AMF may be an initial AMF.

In operation 503, a general registration procedure may be performed.

In operation 505, the AMF may send an authorization/subscription checkrequest to the UDM with the NSSAI.

In operation 507, the UDM may check whether the UE is allowed to use arequested network slice instance (NSI) based on the NSSAI.

In operation 509, the UDM may send an authorization/subscription checkresponse to the AMF with the accepted NSSAI. That is, the AMF mayacquire the accepted NSSAI from the UDM and accordingly, may determinepotential accepted S-NSSAI.

In operation 511, the AMF may send an NSI selection request to the NSSFwith the accepted NSSAI.

In operation 513, the NSSF may determine the availability of therequested NSI based on the accepted NSSAI. If the NSSF detects a moreappropriate AMF capable of providing the selected NSI than a currentAMF, that is, the AMF that sends the NSI selection request to the NSSF,the NSSF may provide information about the new AMF to the current AMF.

In operation 515, the NSSF may forward information about the selectedNSI to the AMF as an NSI selection response. Also, the NSSF may alsoforward information about the new AMF to the AMF as the NSI selectionresponse.

If the current AMF determines to relocate a serving AMF for the UE, theAMF may trigger an AMF relocation procedure based information about thenew AMF provided from the NSSF.

In operation 519, the general registration procedure may be performed.

In operation 521, the AMF may send a registration accept message to theUE with the accepted NSSAI.

That is, in the UE registration procedure, the AMF may acquire theaccepted NSSAI from the UDM and may determine a set of potentialaccepted S-NSSAI. The availability of a network slice instance accordingto the serving registration area of the UE may be determined byverifying the set of potential accepted S-NSSAI through the NSSF.

The accepted NSSAI may be a result of validating the registrationrequest from the UE in terms of the authorization/subscription checkthat is performed through consultation with the UDM that provides a listof authorized NSSAI, and the availability of the network slice instancethat is performed through consultation with the NSSF that is provided byOA&M. Also, the accepted NSSAI may be altered based on a result of theNSI availability check at the NSSF as well as the subscription check.

After an initial slice selection or upon a successful attachmentregistration, the UE may be provided with a temporary ID that is used bythe UE in an RRC connection establishment of a subsequent initial accessso that the RAN may route a NAS message to an appropriate AMF as long asthe temporary ID is valid. Also, the serving PLMN may return acceptedNSSAI that includes a PLMN ID of the serving PLMN. The accepted NSSAImay include S-NSSAI values of network slice instances that are acceptedby the PLMN for the UE to use. Here, it is assumed that a RAN and coreslicing-related configuration does not change within a registration areaof the UE.

For enabling routing of NAS signalling to correct CN functions, the UEmay include NSSAI stored for the PLMN and a complete temporary ID in anRRC. If the RAN is aware of and capable of reaching the AMF associatedwith the temporary ID, the RAN may forward the request to this AMF.Otherwise, the RAN may select an appropriate AMF based on the NSSAIprovided from the UE, and may forward the request to the selected AMF.If the RAN is incapable of selecting the AMF based on the acceptedNSSAI, the request may be sent to a default AMF.

The UE may need to include, in a PDU session establishment request NASmessage, S-NSSAI that enables selection of an SMF with a DNN of a datanetwork for a PDU session.

The RAN needs to be aware of a network slice used by the UE so that theRAN may select an appropriate resource for supporting network slicing inthe RAN.

The UE may cause a network to change a set of slice instances the UE isusing by submitting a new value of NSSAI in a registration requestprocedure. A final decision of a set of network slices allocated to theUE may be made by the network system.

The network system may change a set of network slice instances that arebeing used by the UE by providing the UE with a notification of acceptedNSSAI change based on local policies, subscription changes, and/or UEmobility. This may trigger a UE-initiated registration procedure thatincludes, in RRC and NAS signalling, a value of new accepted NSSAIprovided from the network system.

Changing a set of network slice instances initiated by the UE or thenetwork may lead to changing an AMF based on an operator's policy.Changing a set of network slice instances accessible by the UE may causetermination of an ongoing PDU session with an original set of networkslices if the network slice instances are not longer used. Here, someslices may be still retained potentially, that is, available.

During the initial registration procedure, when the network systemdetermines that the UE needs to be served by another AMF, the AMF havingreceived the initial registration request needs to redirect the initialregistration request to a target AMF through the RAN or through directsignalling between the initial AMF and the target AMF. A redirectionmessage sent from the AMF through the RAN may include information aboutthe target AMF to serve the UE.

With respect to a UE that is already registered, the network systemneeds to support redirection of a UE from a serving AMF to a target AMF.The operator policy may be used to determine whether redirection betweenAMFs is allowed.

When the network system determines to redirect the UE due to the NSSAIchange, the network system may send, to the UE, (a) updated/new NSSAIusing a registration update required procedure and (b) an indication forthe UE to initiate a registration update procedure with the updated/newNSSAI.

The AMF may select an SMF in a network slice instance based on S-NSSAI,a DNN, and other information, for example, UE subscription and localoperator policies. The selected SMF may set a PDU session based onS-NSSAI and the DNN.

FIG. 6 illustrates an example of selecting a network slice instance anda network function instance in a PDU session establishment procedureaccording to an example embodiment.

A communication method performed by a user equipment and a communicationapparatus according to an example embodiment will be described withreference to FIG. 6. In FIG. 6, the UE refers to the user equipment andan AMF, an NSSF, an NRF, and an SMF may indicate network functioninstances included in the communication apparatus.

In operation 601, the UE may send a PDU session establishment request tothe AMF with S-NSSAI through a RAN.

In operation 603, the AMF may send an NSI selection request to the NSSFwith accepted S-NSSAI and an active network slice instance (NSI)accessed by the UE.

In operation 605, the NSSF may select a network slice instancecorresponding to a serving registration area of the UE.

In operation 607, the NSSF may respond to the AMF for a selected servingnetwork serving instance (NSI) and a serving NRF corresponding to theselected NSI.

In operation 609, the AMF may select an SMF through interaction with theserving NRF corresponding to the selected NSI.

In operation 611, a UE-request PDU session establishment may beperformed.

That is, when performing the PDU session establishment, the AMF mayverify a set of potential accepted S-NSSAI through the NSSF to determinethe availability of a network service instance according to the servingregistration area of the UE. Also, the AMF may provide active NSIinformation accessed by the UE to the NSSF. The NSSF may provideinformation about the selected NSI and the serving NRF corresponding tothe selected NSI to the AMF as a response.

FIG. 7 illustrates an example of a repository according to an exampleembodiment.

FIG. 7 illustrates an NFI repository 710 and a serving NF repository720.

An NRF may manage the NFI repository 710 and the serving NF repository720. The NFI repository 710 may include information about networkfunction instances in a network system. For example, the NFI repository710 may include an NFI ID, an NF type, an NSI ID, and an FQDN/IP. TheNFI ID denotes an instance of a corresponding network function instance,and the NSI ID denotes an ID of a network slice instance that includesthe corresponding network function instance.

The NFI repository 710 may be updated by an Operations, Administrationand Management (OAM). In detail, NSI orchestration included in the OAMmay perform a network slice (NS) instantiation and a network sliceinstance (NSI) update and termination. Also, NFI orchestration includedin the OAM may perform a network function (NF) instantiation, an NFIupdate and termination, and an NFI scaling and migration.

An NFI selection may be performed based on information included in theNFI repository 710. In response to an occurrence of the NFI selection,the NRF may store information about the selected NFI in the serving NFrepository 720. That is, the serving NF repository 720 may includeinformation about the serving NFI selected for the UE. An NFI includedin the serving NF repository 720 may constitute a service instance.

The NRF may support a service discovery function. In response to an NFdiscovery request received from a network function instance, the NRF mayprovide information about the discovered network function instance tothe network function instance that requests NF discovery.

In addition to a network function type, a logical network identifier maybe provided to the NRF so that the NRF may support a network functionselection and discovery operation regardless of whether network slicingis present. In the case of network slicing, the logical networkidentifier indicates an NSI ID and otherwise, the logical networkidentifier indicates a serving PLMN.

FIGS. 8 through 10 illustrate examples of an NSI selection and an NFIselection in a network slicing architecture according to an exampleembodiment.

The NSI selection and the NFI selection will be described with referenceto FIG. 8.

UE1 810 may access a CN network slice instance A 820 and networkfunction instances, for example, MM1, SM1, and PC1 selected by a CNthrough a RAN. An NSI selection procedure for a UE may be performedbased on NSSAI configured for the UE. The UE may report the NSSAI to anetwork. A network slice instance may be selected based on the NSSAIprovided from the UE and other information, for example, subscriptiondata, available in the network.

The network slice instance for the UE may be selected based on arequired application and a type of service. A selection of the networkslice instance may consider elements, such as UE functionality,configuration, and authorization.

Through the NSI selection and the NFI selection, an appropriate networkfunction instance capable of providing a specific service within aselected network slice may be selected based on a predeterminedselection condition.

The selection condition may indicate NSSAI. The NSSAI may include an SSTand an SD. The examples of SST include an enhanced mobile broadband(eMBB) service, a critical communications (CriC) service, and a massivemachine type communication mMTC service,

The network system may use the NSSAI with other information, forexample, subscription data, available in the network to select anappropriate network slice instance and network function instance.Hereinafter, mechanisms for the NSI selection and the NFI selection willbe described.

Two-Step Selection Mechanism

As a first step, an NSI selection function may select an appropriatenetwork slice instance within a CN based on NSSAI with information, forexample, subscription data, available in the network. As a second step,an NFI selection function may select an appropriate network functioninstance within the network slice instance selected in the first stepbased on resource operation policies and the like.

One-Step Selection Mechanism

The NSI selection function may select a network slice instance and anetwork function instance per each network function type for a UE basedon an SST and an SD with information, for example, subscription data,available in the network, and may direct the selected network sliceinstance and network function instance to the UE.

Also, the NFI selection function may collect QoS attributes, forexample, a delay and a throughput, of a network function instance, andmay also select a network function instance for the UE from the networkslice instance using the QoS attributes.

FIG. 9 illustrates a function of selecting a network slice instance anda network function instance in a CN according to an example embodiment.

Referring to FIG. 9, a UE1 may forward NSSAI to a core network (CN) 910through a RAN, and a NSI selection 911 may be performed based on theNSSAI, and an NFI selection 913 may be performed. Here, the NSIselection 911 may be performed by an NSSF and the NFI selection 913 maybe performed by an NRF. In detail, the NRF may perform NFI selection andNFI discovery.

Here, a network slice management and orchestration 920 may monitornetwork function instances, for example, NFa#1, NFb#1, and NFc#1,included in a network slice instance. NSSF may perform the NSI selection911 based on a monitoring result and NRF may perform the NFI selection913 based on the monitoring result. For example, the monitoringoperation may be performed to obtain QoS attributes of each of thenetwork function instances and may be represented as indicated withalternated long and short dash lines of FIG. 9.

Once the NFI selection 913 is performed, entry update may be performed.A result of the NSI selection 911 and the NFI selection 913 may bestored in a serving NF repository 915.

A network function instance may be selected from the network sliceinstance based on redundancy, expandability, capability, and the like.Accordingly, there is a need to determine a set of corresponding networkfunction instances per UE service request based on a policy of a networkoperator. In addition, the NFI selection 913 may be performed by furtherconsidering load balancing, resource optimization, energy efficiency,and the like. That is, redundancy, expandability, capability, loadbalancing, resource optimization, energy efficiency, and the like may beconsidered as a policy of a network operator.

The network slice management and orchestration 920 may provide aresource operation policy of the network operator, may provide QoSattributes of the network function instance, and may manage a lifecycleof the network function instance.

FIG. 10 illustrates an NRF 1010 to perform an NFI selection/discoveryfunction according to an example embodiment.

Referring to FIG. 10, the NRF 1010 may manage a selection result of anetwork function instance, and may perform discovery for the selectednetwork function instance in response to a request from the networkfunction instance.

A plurality of instances for a network function may be provided withinthe network slice instance for redundancy, expandability, and the like.That is, a plurality of instances for the same network function may havedifferent QoS attributes, for example, capability, performance, and thelike. An appropriate network function instance may be selected from thenetwork slice instance based on QoS attributes of network functioninstances. Alternatively, a network function instance may be reselectedto meet a specific QoS attribute.

This NFI selection may be based on the following rules.

A network slice instance may include a plurality of network functioninstances for a specific service with network capabilities. A networkslice instance per requested UE service may be selected based on“network slice selection assistance information” (NSSAI). Two or morenetwork function instances per each network function type may beprovided for capability, duplication, expandability, and the like,within the network slice instance. A set of network function instancesmay be selected per UE service request for binding. An NFI selection maybe performed according to a policy of the network operator, for example,energy efficiency, load balancing, resource optimization, and the like.Binding information of the selected network function instance may beadditionally provided to the NRF 1010. For roaming, a set of networkfunction instances may be updated by reselecting the network functioninstance or by changing QoS attributes of the network function instance,the policy of the network operator, roaming, and the like.

An NSSF may select an appropriate network slice instance based on theNSSAI. In detail, the NSSF may determine a target network slice instanceclassified into a service type requested from the UE and may select anetwork slice instance based on a variety of UE and network-providedNSSAI. For example, the NSSAI may include UE subscription data, thepolicy of the network operator, and the like.

The NRF 1010 may select an appropriate network function instance basedon resource operational policies of the network operator, for example,load balancing, resource optimization, and the like. In detail, the NRF1010 may identify a network function (NF) or an NF type of a givennetwork slice instance, may determine a single instance from among aplurality of instances of each NF or NF type within the given networkslice instance, and may store binding information of the selectednetwork function instances in a serving NF repository of the NRF 1010.

FIG. 11 illustrates a communication apparatus according to an exampleembodiment.

Referring to FIG. 11, a communication apparatus 1100 includes a memory1110 and a processor 1120. The memory 1110 and the processor 1120 maycommunicate with each other through a bus 1130.

The memory 1110 may include computer-readable instructions. In responseto execution of the instructions stored in the memory 1110 at theprocessor 1120, the processor 1120 may perform the aforementionedoperations. The memory 1110 may be a volatile memory or a non-volatilememory.

The processor 1120 may execute instructions or programs, or may controlthe communication apparatus 1100. The communication apparatus 1100 maybe configured as a portion of various computing apparatuses. Inaddition, the processor 1120 may process the aforementioned operationsin relation to the communication apparatus 1100.

In the case of a UE registration, the processor 1120 may receive aregistration request from a UE, may select a network slice instance tobe allocated to the UE from among a plurality of network slice instancesin the communication apparatus 1100 in response to the registrationrequest, and may forward a registration accept message corresponding tothe selection of the network slice instance to the UE. Here, the networkslice instance may be in an instantiated form of a network slice thatincludes at least one network function and resource for providing anetwork service having a predetermined capability and characteristic tothe UE.

Also, in the case of a PDU session establishment, the processor 1120 mayreceive a PDU session establishment request from the UE, may select anetwork slice instance to be allocated to the UE from among theplurality of network slice instances in the communication apparatus 1100in response to the PDU session establishment request, and may select anetwork function instance to be allocated to the UE from among aplurality of network function instances included in the selected networkslice instance. Here, the network slice instance may be in aninstantiated form of a network slice that includes at least one networkfunction and resource for providing a network service having apredetermined capability and characteristic to the UE.

The description made above with reference to FIGS. 1 through 10 may beapplicable to the respective components of FIG. 11 and a furtherdescription is omitted here.

FIGS. 12 and 13 are flowcharts illustrating a communication methodaccording to an example embodiment.

A communication method of a communication apparatus that performscommunication with a UE in a UE registration according to an exampleembodiment will be described with reference to FIG. 12.

Referring to FIG. 12, in operation 1210, the communication apparatusreceives a predetermined request from the UE. NSSAI may be included inthe request. For example, the request may be a registration request.

In operation 1220, the communication apparatus selects a network sliceinstance to be allocated to the UE from among the plurality of networkslice instances in the communication apparatus in response to therequest. The communication apparatus may select the network sliceinstance to be allocated to the UE based on the NSSAI included in therequest.

The NSSAI may include (a) an SST requested from the UE or (b) the SSTand an SD corresponding to the UE. The SST may indicate an expectednetwork behavior in terms of a service requested from the UE. The SD maycomplement the SST to select a single network slice instance from amonga plurality of network slice instances that comply with the SST inresponse to the plurality of network slice instances complying with theSST. The SD may include at least one of an area in which the UE islocated, subscription data of the UE, QoS attributes of the plurality ofnetwork slice instances, and terminal characteristics.

The communication apparatus may select the network slice instance to beallocated to the UE by further using at least one of the network sliceinstance pre-allocated to the UE and a serving registration area of theUE.

In operation 1230, the communication apparatus forwards a response tothe request to the UE in response to the selection of the network sliceinstance. For example, the response to the request may be a registrationaccept message.

Also, in response to a detection of a new AMF further appropriatecompared to a current AMF to provide the selected network slice instanceto the UE, the communication apparatus may perform relocation from theAMF to the new AMF. When the plurality of network slice instances isallocated to the UE, an AMF and an NSSF included in the communicationapparatus may be shared between the plurality of network slice instancesallocated to the UE.

FIG. 13 illustrates a communication method of a communication apparatusthat performs communication with a UE in a PDU session establishmentaccording to an example embodiment.

Referring to FIG. 13, in operation 1310, the communication apparatusreceives a predetermined request from the UE.

In operation 1320, the communication apparatus selects a network sliceinstance to be allocated to the UE from among a plurality of networkslice instances in the communication apparatus in response to therequest. For example, the request may be a protocol data unit (PDU)session establishment request.

The communication apparatus may select the network slice instance to beallocated to the UE based on NSSAI that is included in the request.

The NSSAI may include (a) an SST requested from the UE or (b) the SSTand an SD corresponding to the UE. The SST may indicate an expectednetwork behavior in terms of a service requested from the UE. The SD maycomplement the SST to select a single network slice instance from amonga plurality of network slice instances that comply with the SST inresponse to the plurality of network slice instances complying with theSST. The SD may include at least one of an area in which the UE islocated, subscription data of the UE, QoS attributes of the plurality ofnetwork slice instances, and terminal characteristics.

The communication apparatus may select the network slice instance to beallocated to the UE by further using at least one of the network sliceinstance pre-allocated to the UE and a serving registration area of theUE.

In operation 1330, the communication apparatus selects a networkfunction instance to be allocated to the UE from among a plurality ofnetwork function instances included in the selected network sliceinstance. The communication apparatus may select the network functioninstance to be allocated to the UE based on a logical network identifierindicating the selected network slice instance and a type of a networkfunction indicating a role of the corresponding network functioninstance. The communication apparatus may select a single networkfunction instance per type of a network function from among theplurality of network function instances included in the selected networkslice instance. The communication apparatus may select the networkfunction instance to be allocated to the UE by further considering apolicy of the network operator that provides the network slice instance.

Also, the communication apparatus may select the network functioninstance based on a selection condition received by a serving NRFcorresponding to the selected network slice instance from asource-network function instance that requests the selection of thenetwork function instance. That is, the NRF-driven NH selection may beperformed.

Also, the communication apparatus enables the source-network functioninstance receiving a selectable NFI list from the serving NRFcorresponding to the selected network slice instance to select thenetwork function instance and to forward information about the selectednetwork function instance to the serving NRF. That is, the NF-driven NFIselection may be performed. In detail, the source-network functioninstance may request an NRF for a list of destination-network functioninstances (D-NFIs). In response to the request, the NRF may return IPaddresses of D-NFIs within a corresponding network slice instance. Thesource-network function instance may select a single D-NFI from the listreceived from the NRF and may manage a state.

The network slice instance may be in an instantiated form of a networkslice that includes at least one network function and resource forproviding a network slice having a predetermined capability andcharacteristic to the UE.

The description made above with reference to FIGS. 1 through 11 may beapplicable to the respective operations of FIGS. 12 and 13, and afurther description is omitted.

According to an aspect of at least one example embodiment, terms anddefinitions which is used in specification may be given as below:

5G Access Network: An access network comprising a 5G-RAN and/or non-3GPPAN connecting to a 5G Core Network.

5G Core Network: The core network specified in the present document. Itconnects to a 5G Access Network.

5G QoS Flow: The finest granularity for QoS forwarding treatment in the5G System. All traffic mapped to the same 5G QoS Flow receive the sameforwarding treatment (e.g. scheduling policy, queue management policy,rate shaping policy, RLC configuration, etc.). Providing different QoSforwarding treatment requires separate 5G QoS Flow.

5G QoS Indicator (5QI): A scalar that is used as a reference to aspecific QoS forwarding behaviour (e.g. packet loss rate, packet delaybudget) to be provided to a 5G QoS Flow. This may be implemented in theaccess network by the 5QI referencing node specific parameters thatcontrol the QoS forwarding treatment (e.g. scheduling weights, admissionthresholds, queue management thresholds, link layer protocolconfiguration, etc.).

5G-RAN: A radio access network that supports one or more of thefollowing options with the common characteristics that it connects to5GC:

1) Standalone New Radio.

2) New Radio is the anchor with E-UTRA extensions.

3) Standalone E-UTRA.

4) E-UTRA is the anchor with New Radio extensions.

5G System: 3GPP system consisting of 5G Access Network (AN), 5G CoreNetwork and UE.

Allowed NSSAI: an NSSAI provided by the serving PLMN during e.g. aregistration procedure, indicating the NSSAI allowed by the network forthe UE in the serving PLMN for the current registration area.

Allowed area: Area where the UE is allowed to initiate communication.

Configured NSSAI: an NSSAI that has been provisioned in the UE.

Forbidden area: An area where the UE is not allowed to initiatecommunication.

Initial Registration: UE registration in RM-DEREGISTERED state.

Mobility pattern: Network concept of determining within an NF the UEmobility parameters.

Mobility Registration update: UE re-registration when entering new TAoutside the TAI List.

Network Function: A 3GPP adopted or 3GPP defined processing function ina network, which has defined functional behaviour and 3GPP definedinterfaces.

Non-allowed area: Area where the UE is allowed to initiate registrationprocedure but no other communication.

PDU Connectivity Service: A service that provides exchange of PDUsbetween a UE and a Data Network.

PDU Session: Association between the UE and a Data Network that providesa PDU connectivity service. The type of association can be IP, Ethernetor unstructured.

Periodic Registration update: UE re-registration at expiry of periodicregistration timer.

Requested NSSAI: the NSSAI that the UE may provide to the network.

Service Continuity: The uninterrupted user experience of a service,including the cases where the IP address and/or anchoring point change.

Session Continuity: The continuity of a PDU session. For PDU session ofIP type “session continuity” implies that the IP address is preservedfor the lifetime of the PDU session.

Non-seamless Non-3GPP offload: The offload of user plane traffic viauntrusted non-3GPP access without traversing either N3IWF or UPF.

Network Slicing

A Network Slice may include:

-   -   the Core Network control plane and user plane Network Functions    -   the N3IWF functions to the non-3GPP Access Network

Network slices may differ for supported features and network functionsoptimisations. The operator may deploy multiple Network Slice instancesdelivering exactly the same features but for different groups of UEs,e.g. as they deliver a different committed service and/or because theymay be dedicated to a customer.

A single UE can simultaneously be served by one or more Network Sliceinstances via a 5G-AN. The AMF instance serving the UE logically belongsto each of the Network Slice instances serving the UE, i.e. this AMFinstance is common to the Network Slice instances serving a UE.

A PDU session belongs to one and only one specific Network Sliceinstance per PLMN. Different Network Slice instances do not share a PDUsession, though different slices may have slice-specific PDU sessionsusing the same DNN.

Identification and Selection of a Network Slice: The S-NSSAI and theNSSAI

An S-NSSAI (Single Network Slice Selection Assistance information)identifies a Network Slice.

An S-NSSAI is comprised of:

-   -   A Slice/Service type (SST), which refers to the expected Network        Slice behaviour in terms of features and services;    -   A Slice Differentiator (SD), which is optional information that        complements the Slice/Service type(s) to allow further        differentiation for selecting an Network Slice instance from the        potentially multiple Network Slice instances that all comply        with the indicated Slice/Service type. This information is        referred to as SD.

The S-NSSAI can have standard values or PLMN-specific values. S-NSSAIswith PLMN-specific values are associated to the PLMN ID of PLMN thatassigns it. An S-NSSAI shall not be used by the UE in access stratumprocedures in any PLMN other than the one to which the S-NSSAI isassociated.

The NSSAI is a collection of S-NSSAIs (Single Network Slice SelectionAssistance Information). Each S-NSSAI assists the network in selecting aparticular Network Slice Instance. The CN part of a Network Sliceinstance(s) serving a UE is selected by CN.

The (R)AN may use Requested NSSAI in access stratum signalling to handlethe UE Control Plane connection before the 5GC informs the (R)AN of theAllowed NSSAI. The Requested NSSAI is not used by the RAN for routingwhen the UE provides also a Temporary User ID.

When a UE is successfully registered, the CN informs the (R)AN byproviding the whole Allowed NSSAI for the Control Plane aspects.

When a PDU session for a specific slice instance is established, the CNprovides to the (R)AN the S-NSSAI corresponding to the slice instancethat this PDU session belongs to enable the RAN to perform accessspecific functions.

Subscription Aspects

Subscription data include the S-NSSAI(s) of the Network Slices that theUE subscribes to. One or more S-NSSAIs can be marked as default S-NSSAI.If an S-NSSAI is marked as default, then the network is expected toserve the UE with the related Network Slice even when the UE does notsend any S-NSSAI to the network in a Registration request.

The NSSAI the UE provides in the Registration Request is verifiedagainst the user's subscription data.

UE NSSAI Configuration and NSSAI Storage Aspects

A UE can be configured by the HPLMN with a Configured NSSAI per PLMN. AConfigured NSSAI can be PLMN-specific and the HPLMN indicates to whatPLMN(s) each Configured NSSAI applies, including whether the ConfiguredNSSAI applies to all PLMNs, i. e. the Configured NSSAI conveys the sameinformation regardless of the PLMN the UE is accessing (e.g. this couldbe possible for NSSAIs containing only standardized S-NSSAIs). Whenproviding a Requested NSSAI to the network upon registration, the UE ina given PLMN shall only use S-NSSAIs belonging to the Configured NSSAI,if any, of that PLMN.

Upon successful completion of a UE's Registration procedure, the UE mayobtain from the AMF an Allowed NSSAI for this PLMN, which may includeone or more S-NSSAIs. The Allowed NSSAI shall take precedence over theConfigured NSSAI for this PLMN. The UE shall use only the S-NSSAIs inthe Allowed NSSAI corresponding to a Network Slice for the subsequentnNtwork Slice selection related procedures in the serving PLMN, asdescribed in section 5.15.5.

For each PLMN, the UE shall store the Configured NSSAI and, if any, theAllowed NSSAI. When the UE receives an Allowed NSSAI for a PLMN, itshall store it and override any previously stored Allowed NSSAI for thisPLMN.

Detailed Operation Overview

The establishment of User Plane connectivity to a Data Network via aNetwork Slice instance(s) comprises two steps:

-   -   performing a RM procedure to select an AMF that supports the        required Network Slices    -   establishing one or more PDU session to the required Data        network via the Network Slice Instance(s)

Selection of a Serving AMF Supporting the Network Slices

Registration to a Set of Network Slices

UE with Configured or Allowed NSSAI for the PLMN

When a UE registers with a PLMN, if the UE for this PLMN has aConfigured NSSAI or an Allowed NSSAI f, the UE shall provide to thenetwork in RRC and NAS layer a Requested NSSAI containing the S-NSSAI(s)corresponding to the slice(s) to which the UE wishes to register, inaddition to the Temporary User ID if one was assigned to the UE.

The Requested NSSAI may be either:

-   -   the Configured-NSSAI, or a subset thereof as described below, if        the UE has no Allowed NSSAI for the current PLMN; or    -   the Allowed-NSSAI, or a subset thereof as described below, if        the UE has an Allowed NSSAI for the current PLMN, or    -   the Allowed-NSSAI, or a subset thereof as described below, plus        one or more S-NSSAIs from the Configured-NSSAI for which no        corresponding S-NSSAI is present in the Allowed NSSAI and that        were not previously permanently rejected (as defined below) by        the network for the present tracking area.

The subset of Configured-NSSAI consists of a combination of S-NSSAIsincluding one or more S-NSSAI(s) in the Configured NSSAI applicable tothis PLMN, if the S-NSSAI was not previously permanently rejected (asdefined below) by the network for the present tracking area, or was notpreviously added by the UE in a Requested NSSAI.

The subset of Allowed NSSAI consists of a combination of S-NSSAIsincluding one or more S-NSSAI(s) in the last Allowed NSSAI for thisPLMN.

The UE may provide in the Requested NSSAI an S-NSSAI from the ConfiguredNSSAI that the UE previously provided to the serving PLMN in the currentregistration area.

The UE shall include the Requested NSSAI at RRC Connection Establishmentand in NAS messages. The RAN shall route the NAS signaling between thisUE and an AMF selected using the Requested NSSAI obtained during RRCConnection Establishment. If the RAN is unable to select an AMF based onthe Requested NSSAI, it routes the NAS signalling to an AMF from a setof default AMFs.

Upon successful Registration, the UE is provided with a Temporary ID bythe serving AMF. The UE shall include this Temporary ID in any RRCConnection Establishment during subsequent initial accesses to enablethe RAN to route the NAS signalling between the UE and the appropriateAMF.

The serving PLMN may also return a new Allowed NSSAI identifying theNetwork Slices permitted by the serving PLMN for the UE. The UE shallstore this new Allowed NSSAI and override any previously stored AllowedNSSAI for this PLMN.

The network may individually reject an S-NSSAI provided by the UE in theRequested NSSAI with a rejection cause. The network may also indicate ifthe rejection is permanent (e.g. the S-NSSAI is not supported by thePLMN in at least the current registration area) or temporary (e.g. thenNetwork sSlice corresponding to the S-NSSAI is temporarilyunavailable).

When receiving from the UE a Requested NSSAI and a Temporary ID in RRC,if the RAN can reach an AMF corresponding to the Temporary ID, then RANforwards the request to this AMF. Otherwise, the RAN selects a suitableAMF based on the Requested NSSAI provided by the UE and forwards therequest to the selected AMF. If the RAN is not able to select an AMFbased on the Requested NSSAI, then the request is sent to a default AMF.

UE without any NSSAI for the PLMN

When a UE registers with a PLMN, if for this PLMN the UE has noConfigured NSSAI or Allowed NSSAI, the RAN shall route all NASsignalling from/to this UE to/from a default AMF. The UE shall notindicate any NSSAI in RRC Connection Establishment or Initial NASmessage unless it has a Configured NSSAI or Allowed NSSAI for thecorresponding PLMN. Upon successful Registration, the UE is providedwith a Temporary ID by an AMF in this PLMN as well as with an AllowedNSSAI identifying the slices permitted by the serving PLMN for the UE,which are part of the subscribed default S-NSSAI(s) of the UE. The UEshall include this Temporary ID in any RRC Connection Establishmentduring subsequent initial accesses to enable the RAN to route the NASsignalling between the UE and the appropriate AMF.

Modification of the Set of Network Slice(s) for a UE

The set of Network Slices for a UE can be changed at any time while theUE is registered with a network, and may be initiated by the network, orthe UE under certain conditions as described below.

The network, based on local policies, subscription changes and/or UEmobility, may change the set of permitted Network Slice(s) to which theUE is registered. The network may perform such change during aRegistration procedure or trigger a notification towards the UE of thechange of the supported Network Slices using an RM procedure (which maytrigger a Registration procedure). The Network provides the UE with anew Allowed NSSAI and Tracking Area list.

In order to change the set of S-NSSAIs being used, the UE shall initiatea Registration procedure.

Change of set of S-NSSAIs to which the UE is registered (whether UE orNetwork initiated) may lead to AMF change subject to operator policy.

AMF Relocation Due to Network Slice(s) Support

During a Registration procedure in a PLMN, in case the network decidesthat the UE should be served by a different AMF based on NetworkSlice(s) aspects, then the AMF that first received the RegistrationRequest shall redirect the Registration request to another AMF via theRAN or via direct signalling between the initial AMF and the target AMF.The redirection message sent by the AMF via the RAN shall includeinformation for selection of a new AMF to serve the UE.

For a UE that is already registered, the system shall support aredirection initiated by the network of a UE from its serving AMF to atarget AMF due to Network Slice(s) considerations. Operator policydetermines whether redirection between AMFs is allowed.

Establishing Connectivity PDU Session to the Required Network SliceInstance(s)

The establishment of a PDU session in a Network Slice to a DN allowsdata transmission in a Network Slice. A Data Network is associated to anS-NSSAI and a DNN.

The network operator may provision the UE with Network Slice selectionpolicy (NSSP). The NSSP includes one or more NSSP rules each oneassociating an application with a certain S-NSSAI. A default rule whichmatches all applications to a S-NSSAI may also be included. When a UEapplication associated with a specific S-NSSAI requests datatransmission, then:

-   -   If the UE has one or more PDU sessions established corresponding        to the specific S-NSSAI, the UE routes the user data of this        application in one of these PDU sessions, unless other        conditions in the UE prohibit the use of these PDU sessions. If        the application provides a DNN, then the UE considers also this        DNN to determine which PDU session to use. If the UE does not        have a PDU session established with this specific S-NSSAI, the        UE requests a new PDU session corresponding to this S-NSSAI and        with the DNN that may be provided by the application. In order        for the RAN to select a proper resource for supporting network        slicing in the RAN, RAN needs to be aware of the Network Slices        used by the UE.

The AMF selects an SMF in a Network Slice instance based on S-NSSAI, DNNand other information e.g. UE subscription and local operator policies,when the UE triggers the establishment of a PDU session. The selectedSMF establishes a PDU session based on S-NSSAI and DNN.

NRF

The NF Repository Function (NRF) supports the following functionality:

-   -   Supports service discovery function. Receive NF Discovery        Request from NF instance, and provides the information of the        discovered NF instances (be discovered) to the NF instance.

Network Function Discovery and Selection

The NF discovery enables one NF discover a specific target NF type.

Unless the expected NF information is locally configured on requesterNF, e.g. the expected NF is in the same PLMN the NF discovery isimplemented via the NRF. The NF repository function (NRF) is the logicalfunction that is used to supports the functionality of NF discovery.

In order to access to a requested type NF and no associated NF(s) storedon the requester NF, the requester NF initiates the NF discovery byproviding the type of the NF (e.g. SMF, PCF) and other serviceparameters e.g. slicing related information to discover the target NF.

The NRF provides the IP address or the FQDN of NF instance(s) to therequester NF for target NF instance selection. Based on thatinformation, the requester NF can select one NF instance.

For NF discovery across PLMNs, the requester NF provides the NRF thePLMN ID of the target NF. The Local PLMN interacts with the NRF in thetarget PLMN to retrieve the IP address or the FQDN of the target NFinstance (s).

NRF Services

“NF Discovery” Service

Service description: provides the IP address or FQDN of the expected NFinstance(s) to the requester NF.

Input: NF type of the target NF, NF type of the requester NF, PLMN ID ofthe PLMN target NF belongs to, service related information.

Output: a set of target NF instance(s).

Service procedure is shown on FIG. 14.

In operation 1410, the Requester-A NF needs to discover the expected NFinstance(s). For example, the AMF requests to discover the SMFinstance(s) in the same PLMN. The Requester-A sends NF Discovery Requestto NRF in the same PLMN, including: NF Type of the expected NF instance,NF type of the requester, Network Slice related information (optional),and other service related parameters.

In operation 1420, the NRF authorizes the NF Discovery Request. Based onthe profile of the expected NF and the type of the requester NF, the NRFdetermines whether the requester NF is allowed to discover the expectedNF instance(s). If the expected NF instance(s) are deployed in onenetwork slice, NRF authorizes the discovery request according to thediscovery configuration of the Network Slice, e.g. the expected NFinstance(s) are only discoverable by the NF in the same network slice.

In operation 1430, if allowed, the NRF determines the discovered NFinstance(s) and provides the information of a set of discovered NFinstance(s) to the Requester via NF Discovery Response message. Theinformation of the discovered NF instance(s) include: FQDN or IP addressof the expected NF instance(s).

In case that the requester needs to discover the NF in another PLMN, theNRF in serving PLMN needs to requests “NF Discovery” service from NRF inthe remote PLMN. The procedure is depicted in FIG. 15.

In operation 1510, the Requester-B NF needs to discover the NFinstance(s) in remote PLMN. For example, the AMF requests to discoverthe SMF instance(s) in the remote PLMN. The requester sends NF DiscoveryRequest to NRF, including: NF type of the expected NF, the Remote PLMNID are included in the NF Discovery Request.

In operation 1520, the NRF in serving PLMN identifies NRF in remote PLMNbased on the Remote PLMN ID, and it requests “NF Discovery” service fromNRF in remote PLMN according the procedure in FIG. 5.2.7.1-1 to get theexpected NF instance (s) deployed in the remote PLMN. As the NRF in theserving PLMN triggers the “NF Discovery” on behalf of the Requester-BNF, the NRF in the serving PLMN shall not replace the information of theservice requester NF, i.e. Requester-B NF, in the Discovery Requestmessage it sends to the NRF in remote PLMN.

In operation 1530, the NRF in serving PLMN provides the information of aset of the discovered NF Instance(s) in NF Discovery Response message.

The units and/or modules described herein may be implemented usinghardware components, software components, and/or combination thereof.For example, the hardware components may include microphones,amplifiers, band-pass filters, audio to digital convertors, andprocessing devices. A processing device may be implemented using one ormore hardware device configured to carry out and/or execute program codeby performing arithmetical, logical, and input/output operations. Theprocessing device(s) may include a processor, a controller and anarithmetic logic unit, a digital signal processor, a microcomputer, afield programmable array, a programmable logic unit, a microprocessor orany other device capable of responding to and executing instructions ina defined manner. The processing device may run an operating system (OS)and one or more software applications that run on the OS. The processingdevice also may access, store, manipulate, process, and create data inresponse to execution of the software. For purpose of simplicity, thedescription of a processing device is used as singular; however, oneskilled in the art will appreciated that a processing device may includeplurality of processing elements and plurality of types of processingelements. For example, a processing device may include plurality ofprocessors or a processor and a controller. In addition, differentprocessing configurations are possible, such a parallel processors.

The software may include a computer program, a piece of code, aninstruction, or some combination thereof, to independently orcollectively instruct and/or configure the processing device to operateas desired, thereby transforming the processing device into a specialpurpose processor. Software and data may be embodied permanently ortemporarily in any type of machine, component, physical or virtualequipment, computer storage medium or device, or in a propagated signalwave capable of providing instructions or data to or being interpretedby the processing device. The software also may be distributed overnetwork coupled computer systems so that the software is stored andexecuted in a distributed fashion. The software and data may be storedby one or more non-transitory computer readable recording mediums.

The methods according to the above-described example embodiments may berecorded in non-transitory computer-readable media including programinstructions to implement various operations of the above-describedexample embodiments. The media may also include, alone or in combinationwith the program instructions, data files, data structures, and thelike. The program instructions recorded on the media may be thosespecially designed and constructed for the purposes of exampleembodiments, or they may be of the kind well-known and available tothose having skill in the computer software arts. Examples ofnon-transitory computer-readable media include magnetic media such ashard disks, floppy disks, and magnetic tape; optical media such asCD-ROM discs, DVDs, and/or Blue-ray discs; magneto-optical media such asoptical discs; and hardware devices that are specially configured tostore and perform program instructions, such as read-only memory (ROM),random access memory (RAM), flash memory (e.g., USB flash drives, memorycards, memory sticks, etc.), and the like. Examples of programinstructions include both machine code, such as produced by a compiler,and files containing higher level code that may be executed by thecomputer using an interpreter. The above-described devices may beconfigured to act as one or more software modules in order to performthe operations of the above-described example embodiments, or viceversa.

The components described in the exemplary embodiments of the presentinvention may be achieved by hardware components including at least oneDSP (Digital Signal Processor), a processor, a controller, an ASIC(Application Specific Integrated Circuit), a programmable logic elementsuch as an FPGA (Field Programmable Gate Array), other electronicdevices, and combinations thereof. At least some of the functions or theprocesses described in the exemplary embodiments of the presentinvention may be achieved by software, and the software may be recordedon a recording medium. The components, the functions, and the processesdescribed in the exemplary embodiments of the present invention may beachieved by a combination of hardware and software.

A number of example embodiments have been described above. Nevertheless,it should be understood that various modifications may be made to theseexample embodiments. For example, suitable results may be achieved ifthe described techniques are performed in a different order and/or ifcomponents in a described system, architecture, device, or circuit arecombined in a different manner and/or replaced or supplemented by othercomponents or their equivalents. Accordingly, other implementations arewithin the scope of the following claims.

What is claimed is:
 1. A communication method of a communicationapparatus performing communication with a user equipment, the methodcomprising: receiving a predetermined request from the user equipment;selecting a single network slice instance to be allocated to the userequipment from among a plurality of network slice instances in thecommunication apparatus in response to the request; and selecting asingle network function instance to be allocated to the user equipmentfrom among a plurality of network function instances included in theselected network slice instance, wherein the network slice instance isin an instantiated form of a network slice that includes at least onenetwork function and resource for providing a network service having apredetermined capability and characteristic to the user equipment. 2.The method of claim 1, wherein the selecting of the network sliceinstance comprises selecting the network slice instance to be allocatedto the user equipment based on network slice selection assistanceinformation (NSSAI) included in the request.
 3. The method of claim 2,wherein the NSSAI comprises a slice/service type (SST) requested fromthe user equipment or the slice/service type and a slice differentiator(SD) corresponding to the user equipment.
 4. The method of claim 3,wherein the slice/service type indicates an expected network behavior interms of a service requested from the user equipment.
 5. The method ofclaim 3, wherein the slice differentiator complements the slice/servicetype to select a single network slice instance from among a plurality ofnetwork slice instances that comply with the slice/service type, inresponse to the plurality of network slice instances complying with theslice/service type.
 6. The method of claim 3, wherein the slicedifferentiator comprises at least one of a registration area in whichthe user equipment is located, subscription of the user equipment,quality of service (QoS) attributes of the plurality of network sliceinstances requested, and a terminal characteristic.
 7. The method ofclaim 2, wherein the selecting of the network slice instance comprisesselecting the network slice instance to be allocated to the userequipment by further using at least one of a network slice instancepre-allocated to the user equipment and a serving registration area ofthe user equipment.
 8. The method of claim 1, wherein the selecting ofthe network function instance comprises selecting the network functioninstance to be allocated to the user equipment based on a logicalnetwork identifier indicating the selected network slice instance and atype of a network function indicating a role of the correspondingnetwork function instance.
 9. The method of claim 8, wherein theselecting of the network function instance comprises selecting a singlenetwork function instance for each type of the network function amongthe plurality of network function instances included in the selectednetwork slice instance.
 10. The method of claim 8, wherein the selectingof the network function instance comprises selecting the networkfunction instance to be allocated to the user equipment by further usinga policy of a network operator that provides the network slice instance.11. The method of claim 1, wherein the selecting of the network functioninstance comprises selecting the network function instance based on aselection condition received by a serving network function repositoryfunction (NRF) corresponding to the selected network slice instance froma source-network function instance (S-NFI) that requests the selectionof the network function instance.
 12. The method of claim 1, wherein theselecting of the network function instance comprises selecting, by asource-network function instance (S-NFI) receiving a selectable networkfunction instance list from a serving network function repositoryfunction (NRF) corresponding to the selected network slice instance, thenetwork function instance and forwarding information about the selectednetwork function instance to the serving NRF.
 13. A communication methodof a communication apparatus performing communication with a userequipment, the method comprising: receiving a predetermined request fromthe user equipment; selecting a single network slice instance to beallocated to the user equipment from among a plurality of network sliceinstances in the communication apparatus in response to the request; andforwarding a response to the request to the user equipment in responseto the selection of the network slice instance, wherein the networkslice instance is in an instantiated form of a network slice thatincludes at least one network function and resource for providing anetwork service having a predetermined capability and characteristic tothe user equipment.
 14. The method of claim 13, wherein the selecting ofthe network slice instance comprises selecting the network sliceinstance to be allocated to the user equipment based on network sliceselection assistance information (NSSAI) included in the request. 15.The method of claim 13, further comprising: performing relocation from acurrent access and mobility management function (AMF) to a new AMF inresponse to a detection of the new AMF further appropriate compared tothe current AMF, to provide the selected network slice instance to theuser equipment.
 16. The method of claim 13, wherein an AMF and a networkslice selection function (NSSF) included in the communication apparatusare shared by a plurality of network slice instances allocated to theuser equipment in response to the plurality of network slice instancesbeing allocated to the user equipment.
 17. A communication apparatuscomprising: a processor; and a memory comprising at least oneinstruction executable at the processor, wherein, in response to anexecution of the at least one instruction at the processor, theprocessor is configured to receive a predetermined request from a userequipment, to select a single network slice instance to be allocated tothe user equipment from among a plurality of network slice instances inthe communication apparatus in response to the request, and to select asingle network function instance to be allocated to the user equipmentfrom among a plurality of network function instances included in theselected network slice instance, and the network slice instance is in aninstantiated form of a network slice that includes at least one networkfunction and resource for providing a network service having apredetermined capability and characteristic to the user equipment. 18.The communication apparatus of claim 17, wherein the processor isconfigured to select the network slice instance to be allocated to theuser equipment based on network slice selection assistance information(NSSAI) included in the request.
 19. The communication apparatus ofclaim 17, wherein the processor is configured to select the networkslice instance to be allocated to the user equipment by further using atleast one of the network slice instance allocated to the user equipmentand a serving registration area of the user equipment.